numfmt can output grouped digits: $ numfmt --grouping 1000 1,000
but it cannot accept back its own output: $ numfmt --grouping 1000 | numfmt numfmt: invalid suffix in input: ‘1,000’ This has been address a few times before: - http://lists.gnu.org/archive/html/coreutils/2013-02/msg00000 - http://lists.gnu.org/archive/html/coreutils/2012-12/msg00077 - http://lists.gnu.org/archive/html/coreutils/2012-12/msg00057
